System of frequency transformation



E. F. W. ALEXANDERSON.

SYSTEM OF FREQUENCY TRANSFORMATION.

APPLICATION FILED DEC- 6. 1917.

1,316,995. I PatentedSept. 23,1919. 4

Inventor":

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UNIT D STATES PATENT OFFICE.

ERNST F. W. ALEXANDERSON, OF SCHENECTADY, YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

SYSTEM OF FREQUENCY TRANSFORMATION.

Specification of Letters Patent.

Patented Sept. 23, 1919.

Application filed December 6, 1917. Serial No. 205,736.

To all whom it may concern:

Be it known that I, ERNST F. W. ALEX- ANDERSON, a citizen of the United States, residing at Schenectady, in, the countyof Schenectady, State of New York, have invented certain new and useful Improvements in Systems of Frequency Transformation.

My present invention relates to the transformation of an alternating current of a given frequency into an alternating current of a different frequency and to the utilization of the current thus transformed for radio signaling purposes.

proposed for transforming an alternating current of fundamental frequency into an alternating current ofa frequencyharmonic to the fundamental frequency. In some of these systems means have been provided 'for distorting the wave of the current of funds. mental frequency from the sine wave form in such: a way that certain harmonics are made prominent and these harmonics have been segregated in circuits which are resonant to the particular harmonic or harmonics which are to be utilized.

One of the objects of my invention is to improve and simplify the operation of a system of the type mentioned. A further object of my invention is to provide a simple and eflicient means for impressing an alternating current of harmonic frequency upon a radiating system for radio signaling pur poses. A third object of my invention is to provide a simple and eflicient method for controlling the current in the radiating system in order to produce the desired signals therein.

In prior systems of the type in question, it has usually been customary to tune the circuit of the fundamental frequency by means of a condenser in series with the source of supply and the iron core inductance which has been employed for distorting the wave form. Such a circuit has a minimum when no current of harmonic frequency is being supplied to the utilization system. I

In carrying out this objectcof my invention I provide in shunt to the source of sup-. ply a capacity of such value as to compensate for the inductance of the circuit at no load. As a result when no energy is being withdrawn from the system the only current flowing therein will be a circulating current between the capacity and inductance and the only energy required for maintaining this current will be that required to supply the energy losses of the circuit.

The novel features which I believeto be characteristic of my invention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its organization and method of operation together with further objects and advantages thereof will best be understood by reference to the following description taken in connection withthe accompanying drawing in which I have illustrated diagrammatically one circuit organization Wherebymy invention may be carried into eiiect. As indicated in the drawing a source of energy, which in the present caseis an alternating current generator 1, supplies current to the winding 2 of the iron core 3. A con denser 4. in series with the alternator 1 compensates for the internal inductance of the alternator. Condenser 5 in shunt to the alternator 1 is of such value as; to compensate for the inductance of the winding 2. The condenser 6 which is in serie with the alternator is of such value as to compensate for the inductance 7 which is also in series with the alternator. With the systcmthus far described it will be apparent that the capacity 5 will draw a leading current from the alternator and the inductance 2 will draw an equal lagging current so that when no current is supplied to the radiating system the actual energy which the alternator is required to supplywill be merely the energy requiredto make up the losses in the circuit. In utilizing this circuit arrangement for supplying current of harmonic frequency to a radiating system the terminal 8 of the alternator is grounded and the point 10 between inductances7 and 9 is connected to the antenna 11. The effect of connecting the radiating system in this way is the same as shunting the inductance 2 by aresistance and hence the alternator 1 will be required to supply additional energy for maintaining current in the radiating system. For various reasons it is undesirable when current of a harmonic frequency is supplied to the antenna that current of the fundamental frequency should also fiow in the antenna. In order to prevent this the inductance 9 is arranged in inductiverelation to the mductance 7 and so proportioned that the point 12 at the end of this inductance is of substantially the samepotential with respect to the fundamental frequency as the earth connection. Inother words, there is a potential of fundamentah frequency impressed upon the harmonic frequency" circuit which is equal and opposite to that nnpressed upon the inductance 2 from the source 1. This-beingthe case there is no tendency for current of the fundamental frequency to flow in the antenna. The antenna circuit is tuned bymeans of the usual variable inductance 13 to' the harmonic frequency which it. is desired to utilize. With the arrangement here shown any desired odd harmonic of the fundamental frequency may be-causedto flow in the antenna 11. If it were-desired to utilize an'even'harmonic it would be necessary to employ a source of direct currentfor saturating the core 3. Theindnctance' 7 offers high impedance to current of the harmonic frequency and hence but little current of harmonic frequency' Wlll 'fiOW in' the fundamental frequency circuit. The condenser 5 will offer a low impedanceto-current of the harmonic frequency and" most of'the harmonic frequency current which does flow through in-- ductanc'e will pass through condenser 5 instead of flowing through the alternator.

In order to" control the amplitude of the antenna current in order to produce signals a shunt circuit may lee provided to the antenna and the impedance of this circuit varied in accordance with the signals which are to be produced. In the present case I have illustrated a system whereby the antenna current maybe varied to produce telephonic signals. The shunt circuit mentioned 'is connected to any suitable point 1a in the loading inductancel3 and comprises a magnetic amplifier or controller of the general type described in my United States Patent #1206543 In the present instance the specific form of amplifier used consists of two iron cores 15 and 16 with windings 1'7 and 18 thereon, theset'wowind ings being connected in parallel with each other'in the shunt circuit. Current for productin'g' anormal saturation of the cores 15 and 16 may be derived from adirect current generator 19 which is connected in series With the windings 17 and 18, as inclicated. A resistance 20 may be inserted in this circuit in order to adjust the satura tion current desired for the most ellicient operation. The condenser 21 is of such value as to offer a comparatively low impedance to the high frequency current but effectually prevents short circuiting of the controlling current through the windings 17 and 18.. A teady current from the generator 19 is also caused to flow through the multiple microphone 22. The field winding 23 of the alternator 1 is divided up into four separate parts and the current which flows through the microphone 22 is led through these separate parts of the field winding 23so that the field winding 23 acts as a steady-ing inductance for the current t-hrouglrthe microphone. When the microphone22 is acted upon by sound waves avariable potential is produced across its terminals and this variablepotential is ap plied to the windings 17 and 18 in order to vary the saturation in the cores 15 and 16 and thus vary the impedance of the shunt circuit. This variable potential is applied through the condensers 2%,whiclr condensers prevent the short circuiting. the steadying microphone current. Condenser 25 in the shunt circuit is so adjusted that the circuit becomes resonant when the antenna current is a minimum.

This general method of modulating a high frequency signaling current is described and claimed in my co-pending application, Serial No. 229,686, filed April 20, 191S,,which is a continuation in part of my co-pending application, Serial No: 63.438, filed November 26, 1915.

lVhile I have described my invention with particular reference to the transmission of telephonic signals, it will be apparent that itis by no means limited to" this particular use but that it may be equally well employed for transmitting telegraphic signals if'desired. It is also apparent that many modifications may be made in the circuit arrangement employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

Means for producing high frequency alternating currents comprising a. source of alternating current ofa fundamental frequency, and an electric circuit connected to sald source, said circuit comprising an air core inductance and an iron core inductance, serles capacity in said circuit for neutralizing the inductance of the source and of the air core inductance and shunt capacity in said circuit for neutralizing the iron core inductance.

'2. The combination in a radio signaling system of a source of alternating current of a fundamental frequency, an electric circuit connected to said source, said circuit comprising an air core inductance and an iron core inductance, series capacity in said circuit for neutralizing the inductance of the source and of the air core inductance, shunt capacity in said circuit for neutralizing the iron core inductance and a radiating antenna system which is resonant to a frequency harmonic to the fundamental frequency associated with the iron core inductance.

3. The combination in a radio signaling system .of a source of alternating current of a fundamental frequency, an electric circuit associated therewith which includes an iron core inductance, a radiatin system which is resonant to a frequency harmonic to the fundamental and which also includes said iron core inductance and means for impressing upon the radiating system a potential of the fundamental frequency which is equal and opposite to that impressed upon the iron core inductance from said source.

4. The combination in a radio signaling system of a source of alternating current'of a fundamental frequency, an electric circuit connected to said source, said circuit comprising an air core inductance and an iron core lnductance, series capacity in said circuit for neutralizing the inductance of the source and of the air core inductance, shunt capacity in said circuit for neutralizing the iron core inductance, a radiating antenna system which is resonant to a frequency harmonic to the fundamental frequency associated with the iron core inductance, and means for impressing upon the radiating antenna system a potential of the fundamental frequency which is equal and opposite to that impressed upon the iron core inductance from said source.

5. The combination in a radio signaling system of a source of alternating current of a fundamental frequency, an electric circuit connected to said source, said circuit comprising an air core inductance and an iron core inductance, series capacity in said circuit for neutralizing the inductance of the source and of the air core inductance, shunt capacity in said circuit for neutralizing the iron core inductance, a radiating antenna system which is resonant to a frequency harmonic to the fundamental frequency associated with the iron core inductance, and a second air core inductance in the radiating antenna system which is so proportioned and related to the first air core inductance that it has impressed upon it a potential of fundamental frequency equal and opposite to that impressed upon the iron core inductance from said source. I

6. The combination in a radio signaling system of an alternating current generator adapted to produce current of a fundamental frequency, a radiating antenna system, means for producing in said antenna system from said generator a current of a frequency 'means for producing in said antenna system from said generator a current of a frequency harmonic to the fundamental, a circuit in shunt to said antenna circuit containing a magnetic amplifier, a source of direct current, an inductance, a microphone, means for supplying current to said microphone from said dlrect current source through said ,inductance, means for supplying a variable current from said microphone to the windings of sa d amplifier, and means for sup plying a constant current to the windings of sad amplifier from said direct current 7 source.

8. Means for producing high frequency alternatmg currents comprising a source of alternating current of a fundamental frequency, an electric circuit connected to said source, said circuit comprising an iron core inductance and a shunt capacity for neutralizing the iron core inductance and a consumption circuit operatively related to said iron core inductance and which is resonant to a frequency harmonic to the fundamental.

9. Means for producing high frequency alternating currents comprising a source of alternating current of a fundamental frequency, an electric circuit connected to said source, said circuit comprising an iron core inductance, a series capacity forneutralizing the internal inductance of the source and a shunt capacity for neutralizing the iron core inductance and a consumption circuit operatively related to said iron core inductance and which is resonant to a frequency harmonic to the fundamental.

10. The combination in a radio signaling system of a source of alternating current of a fundamental frequency, an electric circuit connected to said source, said circuit comprising an iron core inductance and a radiating circuit which is resonant to a. frequency harmonic to the fundamental frequency and which also includes said iron core inductance.

11. Means for producing high frequency alternating currents comprising a source of alternating current of a fundamental frequency and an electric circuit connected to said source, said circuit comprising an iron core inductance, a series capacity for neutralizing the internal inductance of the source and a shunt capacity for neutralizing the iron core inductance, a radiating system associated with said iron core inductance, and means for impressing upon said radiating system a potential of the fundamental frequency which is equal and opposite to that impressedupon the iron core inductance from the source.

12. The combination in a radio signaling system of a source of alternating current of a fundamental frequency, an electric circuit connected to said source, said circuit comprising an iron core inductance, aseries capacity in said circuit for neutralizing part of the inductance of the circuit and a shunt capacity for neutralizing the iron core inductance and a radiating system which is resonant to a frequency harmonic to the fundamental frequency and which also includes said iron core inductance. V

13. The combination in a radio signaling system of a source of alternating current of a fundamental frequency, an electric circuit connected to said source, said circuit comprising an iron core inductance, a' series capacity in said circuit for neutralizing part of the inductance of the circuit and a shunt capacity for neutralizing the iron core inductance, a radiating system which is resonant to a frequency harmonic to the fundamental frequency and which also ineludes said iron core inductance, and means for impressing upon said radiating system a potential .of the fundamental frequency which is equal and opposite to that impressed upon the iron eore inductance from the source.

14. Means for producing high frequency alternating currents comprising a source of alternating current of a fundamental frequency, an electric circuit connected to said source, said circuit comprising an iron core inductance and an air core inductance and a series capacity for neutralizing the air core inductance and a consumption circuit operatively related to said iron core inductance and which is resonant to a frequency harmonic to the fundamental.

15. Means for producing high frequency alternating currents comprising a source of alternating current of a fundamental frequency, an electric circuit connected to said source, said circuit comprising an iron core inductance and an air core inductance, a series capacity for neutralizing the air core inductance and a shunt capacity for neutralizing the iron core inductance and a consumption circuit operatively related to an iron core inductance which is resonant to a frequency harmonic to the fundamental.

In Witness whereof, I have hereunto set my hand this lth day of December, 1917.

ERNST F/WV. ALEXANDER-SON.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. 0. 

